title: High-frequency viscosity and generalized Stokes-Einstein relations in dense suspensions of porous particles.
abstract: We study the high-frequency limiting shear viscosity, η∞, of colloidal suspensions of uncharged porous particles. An individual particle is modeled as a uniformly porous sphere with the internal solvent flow described by the Debye-Bueche-Brinkman equation. A precise hydrodynamic multipole method with a full account of many-particle hydrodynamic interactions encoded in the HYDROMULTIPOLE program extended to porous particles, is used to calculate η∞ as a function of porosity and concentration. The second-order virial expansion for η∞ is derived, and its range of applicability assessed. The simulation results are used to test the validity of generalized Stokes-Einstein relations between η∞ and various short-time diffusion coefficients, and to quantify the accuracy of a simplifying cell model calculation of η∞. An easy-to-use generalized Saitô formula for η∞ is presented which provides a good description of its porosity and concentration dependence.
authors.affiliation: Institute of Theoretical Physics, University of Warsaw, Hoża 69, 00-681 Warsaw, Poland.
authors.forename: Gustavo C
authors.initials: GC
authors.lastname: Abade
authors.forename: Bogdan
authors.initials: B
authors.lastname: Cichocki
authors.forename: Maria L
authors.initials: ML
authors.lastname: Ekiel-Jeżewska
authors.forename: Gerhard
authors.initials: G
authors.lastname: Nägele
authors.forename: Eligiusz
authors.initials: E
authors.lastname: Wajnryb